(Received 4 January 2008;accepted 24 January 2008;online 30 January 2008)

The title compound, [Yb2(CF3O3S)(C10H15)2(OH)2(C12H12N2)2](C24H20B)·C12H12N2, crystallizes as a half-sandwich complex with a bridging trifluoro­methane­sulfonate as well as two bridging hydroxide groups. The bound bipyridine ligands have N—C—C—N torsion angles of 13.1 (9) and −12.1 (8)°. The structure also contains an uncoordinated 5,5′-dimethyl-2,2′-bipyridine molecule with an N—C—C—N torsion angle of 169.5 (7)°. The triply bridged Yb centers are 3.5990 (4) Å apart. The Yb—N bond lengths are in the range 2.389 (6)–2.424 (5) Å.

The title compound, (I), is presented in Fig. 1, wherein, the cyclopentadienyl ligands represented by Cg1 and Cg2, are the centroids of the rings defined by C1—C5 and C6—C10, respectively. The two pyridine rings of the bipyridine (bpy) ligands are not coplanar; the torsion angles N—C—C—N are 12–13°. The Yb(III)-N distances of 2.389 (6)–2.424 (5) Å in (I) are not uncommon for neutral bpy bound to a Ytterbium center (Schultz et al., 2002). The trifluoromethanesulfonate anion is bridging. The uncoordinated 5,5'-dimethyl-2,2'-bipyridine is the second structure (van Albada et al., 2005) of uncoordinated 5,5'-dimethyl-2,2'-bipyridine in the Cambridge Structural Database (Allen, 2002).

Impure NaBPh4 (1.00 g, 3.13 mmol) purchased from Aldrich was added to ([Cp*2Yb(5,5'-dimethyl-2,2'-bipyridine)][OTf] (1.16 g, 1.49 mmol) in the presence of 5,5'-dimethyl-2,2'-bipyridine (0.50 g, 2.71 mmol) in ether. The solution was stirred overnight and the ether was filtered off. The yellow residue was dissolved in dichloromethane, filtered, and then layered with pentane. After 3 days dark yellow crystals were obtained. Yield 0.86 g (77%).

All non-hydrogen atoms were refined anisotropically. Hydrogen atoms bonded to C-atoms were included in the refinements at geometrically idealized positions with C—H = 0.95 Å and Uiso = 1.2 times Ueq of the parent atoms. The hydrxyl H-atoms were located from a difference map and included in the refinements at those positions with Uiso = 1.2 times Ueq of the O-atoms. The final difference map showed residual electron denities in the close proximity of Yb atoms.

Refinement. Refinement using reflections with F2 > 3.0 σ(F2). The weighted R-factor (wR), goodness of fit (S) and R-factor (gt) are based on F, with F set to zero for negative F. The threshold expression of F2 > 3.0 σ(F2) is used only for calculating R-factor (gt).

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